Method of soaking animal hides and skins



NIETHOD F SOAKING ANIMAL HIDES AND SKINS Rudi Heyden and JiirgenPlapper, Dusseldorf, Germany, assignors to Biihme Fettchemie G.m.b.H.,Dusseldorf, Germany, a corporation of Germany No Drawing. ApplicationJanuary 20, 1958 Serial No. 700,768

Claims priority, application Germany January 22, 1957 4 Claims. (Cl.8-94.18)

This invention relates to a novel method of soaking animal hides andskins involving the use of low-molecular mercapto-alkane-sulfonic acidsor their salts in the soaking liquor.

' It is well known that the soaking action of the soaking liquor uponanimal hides and skins in the manufacture of leather articles can besubstantially improved by modifying the soaking liquor with variousadditives. For example, the prior art describes soaking liquors whichcontain small quantities of sodium hydroxide, sodium sulfide, sodiumsulfhydrate or sodium sulfite. However, because of their alkalinity,these additives produce undesirable swelling effects in the animal hideand permit the soaking action to proceed in a pH range in which thebacteria growth is substantially accelerated.

It is also well known that soaking can be accelerated by addingmercapto-carboxylic acids or their salts to the soaking liquor. However,the use of mercapto-carboxylic acid additives also has certaindisadvantages in that the fiber agglutination in high-temperature-driedhides and skins cannot be sufliciently loosened within a reasonableperiod of time with the aid of such modified soaking liquors. Thefinished leather therefore has inadequate fullness, a hard feel and acoarse grain.

It is an object of the present invention to provide an improved methodof soaking hides and skins which will make it possible to accomplish asuflicient loosening of the fiber agglutination within a relativelyshort period of time without undue Swelling and within a pH range inwhich the bacteria growth is held at a minimum.

Other objects and advantages of the present invention will becomeapparent as the description thereof proceeds.

We have discovered that all of the above objects and improvements areachieved and that the shortcomings of the prior art are overcome bysoaking hides and skins, and particularly those which are thick anddifficult to soak through completely, in soaking liquors modified withmercapto-alkane-sulfonic acids or their water-soluble salts.

Examples of mercapto-alkane-sulfonic acids which are eminently suitablefor this purpose are Z-mercapto-ethanesulfonic acid-1,3-mercapto-propane-sulfonic acid-1, 3- mercapto-butane-sulfonic acid-1and 4-mercapto-butanesulfonic acid-1. The mercapto-alkane-sulfonic acidsare preferably employed in the form of their water-soluble salts, suchas their alkali metal or ammonium salts, or their salts formed withorganic bases such as with dimethylamine, triethanolamine anddiethanolamine.

The soaking action of the modified soaking liquor upon the hides andskins may be further enhanced by adding anionic or non-ionic wettingagents thereto.

Optimum results are obtained where the mercaptoalkane-sulfonic acids ortheir salts are added to the soaking liquor in an amount ranging from0.05 to 1.00 gm./ liter. The wetting agents are preferably added inamounts ranging from 0.5 to 1.0 gm./liter.

In addition to the advantages previously mentioned,

2,923,595 Patented Feb. 2, 1960 the mercapto-alkanesulfonic acids havethe advantage over the mercapto-carboxylic acids that the former areetiective at considerably lower concentrations. Despite such loweflective concentrations the soaking rate of the soaking liquorsmodified with the mercapto-alkanesulfonic acids or their water-solublesalts according to the present invention is substantially greater thanthat of soaking liquors modified with mercapto-carboxylic acids or theirsalts.

The following examples will further illustrate the present invention andenable others skilled in the'art to understand the invention morecompletely. It should be understood, however, that'we do-not wish tolimit our invention to the particular examples given herein.

Example I Dried goat skins were drum-soaked in an aqueous solutioncontaining 0.1 gm./liter of the triethanolamine salt of4-mercaptobutane-sulfonic acid-1. After about three days the skins werethoroughly soaked through, as evidenced by a water absorption of about124% by weight based on the weight of the dry skins.

As comparison, dried goat skins were soaked for three days in an aqueoussolution containing 0.5 gm./liter sodium thioglycolate. The waterabsorption was only 107% by weight based on the weight of the dry skins.

Example II Sun-dried bnifalo skins were soaked in an aqueous solutioncontaining 0.5 gm./liter of the dimethylamine salt of3-mercapto-propane-sulfonic acid-1 and 0.2 gm./ liter of a commercialalkylsulfonate wetting agent: After about two days of soaking, the rawhides were thoroughly and uniformly soaked through and the fiberagglutination was excellently loosened.

The same results were obtained when 0.2 gm./liter of a commercialalkylbenzene sulfonate was added as a wetting agent instead of thealkylsulfonate.

Example 111 0.2 gm./liter of the sodium salt ofZ-mercapto-ethanesulfonic acid-1 are used instead of thetriethanol-amine salt of 4-mercaptobutane-sulfonic acid-1 of Example Iwith an analogous soaking efiect.

Example IV 0.5 gm./liter of the ammonium salt of4-mercaptobutane-sulfonic acid-2 are used instead of themercaptoalkane-sulfonic acid salt of Example I with a good soakingaction.

Example V 0.1 gm./liter of the diethanolamine salt of 4-mercapto-Z-methyI-butane-sulfonic acid-2 are used instead of themercapto-alkane-sulfonic acid salt of Example II with a remarkablesoaking eifect.

Example VI While we have illustrated the present invention with the aidof certain specific embodiments, it will be readily apparent to thoseskilled in the art that the invention is not limited to theseembodiments, and that various changes and modifications may be madewithout departing from the spirit of the invention or the scope of thezip-- pended claims. We claim:

1. The method of soaking raw animal hides and skins. which comprisesimmersing said hides and skins in an;

aqueous solution having dissolved therein from 0.05 to 1.00 gm./liter ofcompounds selected from the group consisting of mercapto-loweralkane-sulfonic acids and theirwater-soluble salts.' t r,

2. The method of soaking raw animal skins and hides, which comprisesimmersing said skins and hides in an aqueous solution having dissolvedtherein from 0.05 to 1 00 gm./lite r of a compound selected from thegroup consisting of mercapto-lower alkane-sulfonic acids and theirwater-soluble salts, and from 0.5 to 1.0 gm/liter of wetting agentselected from the group) consisting or anionic and non-ionic wettingagents.

4. The method of soaking dried buffalo hides which comprises immersingsaid hides in an aqueous solution having dissolved therein 0.5 gm./literof the dimethylamine salt of 3-mercapto-propane-sulfonic acid-1 and 0.2gm./1iter of a sulfonate wetting agent selected from the groupconsisting of alkyisulfonates and alkylbenzene sulfonates.

References Cited in the fileof this patent UNITED STATES PATENTS HaefeleOct. 28, 1952 OTHER REFERENCES Progress in Leather Science, 1920-1945,Manufi, LeatherAsso, London, 1948, pp. 138 and 139.

1. THE METHOD OF SOAKING RAW ANIMAL HIDES AND SKINS, WHICH COMPRISES IMMERSING SAID HIDES AND SKINS IN AN AQUEOUS SOLUTION HAVING DISSOLVED THEREIN FROM 0.05 TO 1.00 GM./LITER OF COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF MERCAPTO-LOWER ALKANE-SULFONIC ACIDS AND THEIR WATER-SOLUBLE SALTS. 